backups: add setup/teardown

1. add setup, teardown hooks
2. move the managed mount setup and teardown to filesystem backend
3. remove this vague storage.js

we should convert storageApi into a real object, so we don't have to
keep passing apiConfig around

src/storage/noop.js

@@ -13,6 +13,8 @@ exports = module.exports = {
     remove,
     removeDir,
 
+    setup,
+    teardown,
     cleanup,
 
     testConfig,
@@ -105,6 +107,14 @@ async function testConfig(apiConfig) {
     assert.strictEqual(typeof apiConfig, 'object');
 }
 
+async function setup(apiConfig) {
+    assert.strictEqual(typeof apiConfig, 'object');
+}
+
+async function teardown(apiConfig) {
+    assert.strictEqual(typeof apiConfig, 'object');
+}
+
 function removePrivateFields(apiConfig) {
     return apiConfig;
 }